The legal battle between Republican lawmakers and Attorney General Eric Holder over access to documents in a gun scandal could take months, if not years, to resolve.

But one man has already been sifting through secret emails about the operation known as Fast and Furious. He's Michael Horowitz, the Justice Department's new watchdog.

To hear his former colleagues tell it, Horowitz is no stranger to touchy subjects. He made his name in New York prosecuting corrupt police officers in the city's 30th Precinct, known as the "Dirty 30," recalls former U.S. Attorney Mary Jo White.

"You know, he ended up at the end of the day with dozens of defendants. It was probably the biggest police corruption case in decades," she says, "and he was just brilliant in the way he handled that, very tenacious."

Horowitz, 49, went on to work at Justice Department headquarters in Washington, where he served as chief of staff in the criminal division, at the end of the Clinton years and then under Bush administration official Michael Chertoff.

Chertoff says he recommended Horowitz for the job of inspector general.

"I think he'll pursue the stuff that needs to be pursued," says Chertoff. "He's not going to be unfair or someone who takes cheap shots, but I do think he'll call it like he sees it, even if he steps on some big toes."

Stepping on big toes is pretty much the Horowitz job description. He's in charge of about 450 employees, including 125 federal agents, who sift through allegations of misspending and misconduct at Justice, the FBI and the Bureau of Alcohol, Tobacco, Firearms and Explosives.

"You're dealing with subjects who are in themselves investigators and they tend to be particularly sensitive when the spotlight turns on them," Chertoff explains.

The inspector general has ongoing probes of the FBI's use of controversial surveillance authorities, management of the terrorist watch list, the Justice Department's efforts to address mortgage fraud, and the Civil Rights Division's enforcement of voting laws, across multiple administrations.

Probably the biggest item on the Horowitz agenda is a long-awaited report on Fast and Furious. That's the flawed gun sting in Arizona, where ATF agents lost track of 2,000 guns. Some later turned up at crime scenes, including the killing of U.S. Border Patrol Agent Brian Terry.

The operation and the Justice Department's response ignited a rancorous political battle, culminating in a historic contempt citation against Holder.

House Speaker John Boehner, a Republican from Ohio, told reporters he's preparing to sue Holder to get access to internal documents between February 2011 and December 2011, after Justice authorities sent a letter to Congress that contained inaccurate statements the department later withdrew.

In an interview with NPR, Horowitz says he prizes one value above all others.

"That we come out with a report that is fair, that is focused on the facts, that ignores whatever the issues have been out there in terms of claims or counterclaims," he says. "We've got the evidence in front of us, we've got the documents, we've got the interviews that we have done and we're going to need to report on those fairly, fully and completely."

His report could come out by the end of summer, if all goes according to schedule.

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